Agents that perturb the dynamics of cellular microtubules are proven cell biology tools, antitumor agents, and antifungal agents. Some have also shown promise as inhibitors of angiogenesis. Microtubule dynamics can be altered by small molecules through a variety of mechanisms, including direct interaction with tubulin (typically leading to inhibition of proliferation into microtubules -- aka tubulin polymerization inhibitors; e.g., colchicinoids and vinca alkaloids), direct interaction with microtubules (typically leading to microtubule stabilization; e.g., taxanes), and through interaction with tubulin/microtubule-associated proteins (e.g., estramustine) Although literally thousands of agents are known to inhibit tubulin polymerization, only a handful of agents stabilize microtubules. The taxanes paclitaxel and docetaxel have provided great advances in clinical outcomes, and one or more of the epothilones will soon become part of oncologists' arsenal. All of the known microtubule stabilizers are structurally complex, synthetically challenging small molecules. It would be of great interest to determine if the rich small molecule scaffolds within the MLSCN repositories will provide less synthetically expensive microtubule stabilizers. Traditionally, microtubule stabilizers have been found by low throughput, temperature-controlled turbidimetry screens with bovine or porcine brain tubulin, followed by electron microscopic analysis of the polymer formed and confirmatory cell-based fluorescence microscopy analyses. We have developed a fluorescence cell-based high information content screen that can be performed reproducibly in microtiter plate-based format with robotic liquid handling. The assay provides excellent Z' factors (> 0.8) with low coefficients of variation. Cells are plated on collagen I, allowed to attach overnight, and are then treated with vehicle or test agents for 21 h. After gentle permeabilization, chromatin (Hoechst dye) and microtubules (anti-alpha-tubulin) are labeled with different fluorophores, followed by a digital image analysis that allows for quantitation of the labeled structures in large numbers of cells, leading to excellent statistical measures. Hits will be verified by examination of a concentration range in the cell-based experiments, as well as by the traditional biochemical methods mentioned above. [unreadable] [unreadable] [unreadable]